IPSec Site to Site randomly loses connectivity

Hello,
i had IPSec Site-To-Site with pfSense 1.2.3. Recently i have upgraded to 2.0.1 (using firmware upgrade option in WebGUI). I have upgraded both pfsense boxes. Now there is a connection between them, but randomly loses it. It's still connected but no traffic between them. When i restart racoon its ok again. A few hours later loses it again. It's different period every time. I have PPTP server running with server address not WAN IP. I tried to disabling and enabling PPTP server no difference. Any ideas what might be wrong ?